Propane gas leaks can obviously cause serious problems. For example, fires resulting from such leaks can cause both property damage and personal injury including, in extreme cases, death. Thus, a very real need exists for an approach in testing for such leaks that will effectively protect the homeowner-users of propane gas. Such protection would also be of substantial benefit to the companies that serve such homeowner-users particularly in the area of reducing the spiraling costs of lawsuits involving the leakage of gas into the home of a customer from the propane system. This leakage is often from appliances that have inadvertently been left on at the time of a gas outage in the propane tank. In any event, whatever the cause of such leakage, it is obviously very important to be able to readily determine when there is leakage from the system.
There are strict rules associated with the assembly and servicing of propane systems. The current rules are set out in NFPA Pamphlet 58. Considering the rules that bear on the issues involved with the present invention, NFPA Pamphlet 58, Section 3-2.10 states that "After assembly, piping systems (including hose) shall be tested and proven free of leaks at not less than operating pressure." Section 4.2.1 states that "Before gas is introduced into a system after being shut off, the entire system shall be inspected to determine that there are no open fittings or ends and all manual valves at outlets on equipment are closed and all unused valves at outlets are closed and plugged or capped." Section 4.2.2 states "Immediately after turning on the gas the piping system shall be tested to ascertain that no gas is escaping." In addition, section 4.3.4 describes the proves for purging (emptying of air from) a system that has been opened and states "After the piping has been placed in operation, all equipment shall be purged and then placed in operation as necessary."
Section 4.1.4 of this pamphlet describes the methods of pressure testing and states as follows: "(a) Test pressure shall be measured with a manometer or with a pressure measuring device designed and calibrated to read, record, or indicate a pressure loss due to leakage during the pressure test period. The source of pressure shall be isolated before the pressure tests are made. (b) The test pressure to be used shall be no less than 11/2 time the proposed maximum working pressure, but not less than 3 psig, irrespective of design pressure. Where the pressure exceeds 125 psig, the test pressure shall not exceed a value that produces a hoop stress in the piping greater than 50 percent of the specified minimum yield strength of the pipe. (c) Systems for undiluted liquefied petroleum gases shall withstand the pressure test in accordance with (b) above, or, for single-staged systems operating at a pressure of 1/2 psig or less, shall withstand a test pressure of 9.0.+-.1/2 inch water column for a period of not less than 10 minutes without showing any drop in pressure. If the source of pressure for this test is a liquefied petroleum gas container, the container service valve shall be checked for positive shutoff with leak detector solution prior to the test, or shall be disconnected from the system during the test. (d) Test duration shall be not less than 1/2 hour for each 500 cubic feet of pipe volume or fraction thereof. When testing a system having a volume less than 10 cubic feet or a system in a single-family dwelling, the test duration shall be permitted to be reduced to 10 minutes. For a piping system having a volume of more than 24,000 cubic feet, the duration of the test shall not be required to exceed 24 hours." Finally, Section 4.1.2 (exception) states that "Fuel gas shall be permitted to be used in piping systems operating at pressures of 0.5 psig."
At present, there is no way for a driver-salesman or a service person, hereinafter referred to for convenience as a repairman or repair personnel, to check for leakage as described above without interrupting the gas piping, a process that is very time consuming. Further, this process introduces unwanted air into the system and thus requires such air to be purged.
There are, of course, many systems which use permanent valves and gauges for determining and/or controlling the pressure in the system. Reference is made in this regard to U.S. Pat. Nos. 2,923,312 (Wagner), 4,332,273 (Boyce) and 4,338,793 (O'Hern, Jr.) relating to refrigeration systems and to U.S. Pat. No. 4,702,754 (Blocker) relating to natural gas or propane delivery systems and U.S. Pat. No. 4,183,078 (Sorrell) relating to a combination shut-off and test-injection valve. Briefly considering some of these patents, the Wagner patent discloses a valve tool for charging and discharging refrigeration systems including a tee-adapter for testing gas pressures. The Boyce patent disclosed a leak-proof connector including a valve of the Schrader (or Schroeder) type while the O'Hern, Jr. patent discloses an adapter for a refrigeration system which also uses a normally closed Schrader valve. The Blocker patent discloses a test adapter which permits pressure tests to be carried out on delivery systems for fuel gas, i.e., propane or natural gas.